Cook your rice. Start the rice first so it’s fluffy and ready when the beef is done. Keep it warm.
Whisk the sauce. In a small bowl, combine soy sauce, brown sugar, mirin, rice vinegar, sesame oil, and water.
Stir until the sugar dissolves. In a separate cup, mix cornstarch with equal water to make a slurry and set aside.
Brown the beef. Heat oil in a large skillet over medium-high. Add ground beef, break it up with a spatula, and cook until no longer pink, about 5–7 minutes.
Season lightly with salt and pepper.
Add aromatics. Stir in garlic and ginger. Cook 30–60 seconds until fragrant. If there’s excess grease, drain it off now for a cleaner sauce.
Simmer with teriyaki. Pour the sauce into the skillet and bring to a gentle simmer.
If you like heat, add sriracha or red pepper flakes.
Thicken the sauce. Stir in the cornstarch slurry and cook 1–2 minutes, stirring, until the sauce turns glossy and coats the beef. Taste and adjust seasoning—add a splash more soy for salt, sugar for sweetness, or vinegar for brightness.
Build the bowls. Spoon rice into bowls. Top with teriyaki beef, shredded carrots, cucumbers or snap peas, and green onions.
Finish with sesame seeds. Serve immediately.